1. Field of the invention
The present invention relates to a flared connection structure of a pipe end portion of a metal pipe for carrying out sealing by being brought into press contact with a pressure receiving seat face of a counterpart joint which is used at a connection end portion of a metal pipe having a comparatively slender diameter and a comparatively thin wall arranged to constitute a supply path for feeding oil or feeding air generally in an automobile or various machines and apparatus, particularly to an improvement in a so-to-speak bridge flare having a spool portion with a section substantially in a U-like shape or a V-like shape constituted by outwardly bulging a section of a pipe end portion of a metal pipe.
2. Description of the prior arts
Conventionally, as shown by FIG. 9, a so-to-speak bridge flare 10 is constituted by a spool portion 11 in which an inclined face 11-1 on a front end portion side of a metal pipe Pxe2x80x2 is made to rise, an end face of the front end portion constitutes a pressurizing seat face 11-2 for pressurizing a counterpart joint 12 and an inclined face on the rear side constitutes a pressure receiving seat 11-3 for receiving pressure of a fastening nut 13 and a section of which is bulged outwardly to thereby constitute substantially a U-like shape on the inner side.
Further, when the bridge flare 10 is connected to the counterpart joint 12, the pressurizing seat face 11-2 constituted by the end face of the front end portion side of the spool portion 11 is brought into contact with an inclined pressure receiving seat face 12-1 of the counterpart joint 12 and an outer peripheral screw portion 13-1 of the fastening nut 13 is screwed to a screw portion 12-2 of the counterpart joint 12 to thereby bring the pressurizing seat face 11-2 of the end face of the spool portion 11 into press contact with the pressure receiving seat face 12-1 of the counterpart joint 12 for sealing and connection.
However, in recent years, there is a tendency in which pressure of fluid flowing at inside of a pipe is increased and particularly when the above-described bridge flare is used as a supply path of fuel such as CNG (Compressed Natural Gas), there pose the following problems. That is:
Since the pressure of an inner fluid is high, there is a need of increasing fastening torque of the fastening nut 13. In such an occasion, since a pocket portion 11-4 formed on the inner side of the spool portion 11 is hollowed, the pocket portion 11-4 is deformed by axial force produced by the fastening nut 13 and face pressure produced between the pressurizing seat face 11-2 of the spool portion 11 and the pressure receiving seat face 12-1 of the counterpart joint 12 is difficult to increase.
Since the inclined face on the front end portion side of the spool. 11 is made to rise and the end face of the front end portion side constitutes the pressurizing seat face 11-2, there is a case in which a bent portion 11-5 formed on the outer peripheral side of the rise portion becomes unstable in view of a shape thereof and the pressurizing seat face 11-2 is inaccurately brought into contact with the pressure receiving seat face 12-1 of the counterpart joint 12.
Since the inclined face on the front end portion side of the spool portion is made to rise and the end face of the front end portion side constitutes the pressurizing seat face 11-2, a region capable of being used as a seat face is narrow.
The spool portion 11 is formed by chucking the metal pipe Pxe2x80x2 and pressurizing the end portion in the axial direction by a punch to thereby carry out pressing operation. In pressing the pressurizing seat face 11-2 of the end face, an area thereof which is brought into contact with the punch is extremely narrowed and therefore, large force is exerted on the portion and flaws or the like caused by the punch grow and the portion is significantly roughened by which there is a possibility in which leakage of the inner fluid is caused by deteriorating sealing performance.
The invention resolves the problem of the conventional technology and it is an object thereof to provide a flared connection structure of a pipe end portion in which a pocket portion formed on an inner side of a spool portion is filled with a ring member to thereby increase supporting force and increase face pressure of a seat face, a pressurizing seat face having a stable shape and a wide area can be formed and a roughened face produced by flaws caused in pressing operation is reduced owing to the wide area of the pressurizing seat face portion to thereby promote sealing performance.
In order to achieve the above-described object, according to an aspect of the invention, there is provided a flared connection structure of a pipe end portion comprising a bridge flare having a spool portion having a section substantially in a U-like shape or a V-like shape produced by bulging the section in an outer direction at a pipe end portion of a metal pipe in which other inclined face of the spool portion formed on a rear side of one inclined face on a front end portion side constitutes a pressure receiving seat face, wherein a separate member of a ring member having a section substantially in a U-like shape is interposed in a pocket portion produced between inner sides of the two inclined faces of the spool portion from the one inclined face and a portion of the ring member provided to cover the one inclined face constitutes a pressure receiving seat face opposed to a pressure receiving seat face of a counterpart joint. Further, according to the flared connection structure, there is formed a recessed and projected face in shapes of concentric circles at a portion of the ring member opposed to the one inclined face on the front end portion side of the spool portion having the section substantially in the U-like shape of the V-like shape, or recessed and projected faces in shapes of concentric circles are respectively formed at the portion of the ring member opposed to the one inclined face on the front end portion side of the spool portion having the section substantially in the U-like shape of the V-like shape and the pressurizing seat face of the ring member opposed to the pressure receiving seat face of the counterpart joint, or a recessed and projected face in shapes of concentric circles is formed on the pressure receiving seat face of the counterpart joint opposed to the pressurizing seat face of the ring member. Further, the ring member is formed by being plated with a soft metal of indium, copper or tin or being coated with a resin of fluororesin or the like.